Apparatus for the production of music



Oct, 3, 1933., B ssmgR 11 929931 APPARATUS FOR THE PRODUCTION OF MUSIC Filed May 4. 1931 NVENTOR:

' Patented Oct. 3, 1 933 p UNITED STATES PATENT OFFICE.

APPARATUS FOR THE PRODUCTION OF MUSIC Application May 4, 1931. Serial No. 534,849

9 Claims.

This invention relates to musical instruments and systems wherein the vibrations of tuned bodies are translated into electric oscillations, and more particularly to the control of the damping and amplitude-time characteristics generally of such vibrations. The invention, although useful with any mode of excitation of such tuned bodies, is illustrated in connection with an instrument in which the tuned bodies are caused to 10 vibrate by percussion. Such instruments and im-.

provements therein have been disclosed generally in my co-pending application, Serial Number 512,399; and certain improvements more specifically relating to the translating devices therein have been disclosed in my co-pending applica- I characteristics of all or of a group of such tuned bodies. A further object is the provision of an electrical musical instrument of which the musical notes produced may be caused at will to decay rapidly or slowly or to be fully sustained. Other and allied objects will more fully appear from the following description and the appended claims.

In the detailed description of my invention, hereinafter set forth, reference is had to the accompanying drawing, of which:-

Figure 1 is a view, partly schematic, of a portion of a musical instrument embodying my invention; I Figure 2 is a cross sectional view taken along line 2-2 of Figure l, in which certain further details appear; and

Figure 3 is a schematic drawing of a modified form of my invention.

In Figure 1 I show strings 1, preferably of electrically conductive, magnetic material, strung for example between tuning pins 2 in plank 3 and pins 4 in rear block 5, over triangular bars 6, at least one of which latter may conveniently be electrically conductive in order that the strings may be connected together electrically. There may be employed a hammer 7 underneath each string for vibrating the latter and a damper 16. above each string for stopping the vibration thereof..

Such a hammer 7 and a damper 16'more clearly 5 appear, and actuating means therefor are shown, in Figure 2, a cross sectional view taken along line AA of Figure 1. Keys 17,, pivoted as at 18, may be employed with a repeating action 19, well known in the art as a component of the grand piano, to propel hammer 7 toward string 1 upon depression of the front or left-shown end of the key. Such depression may also serve to raise arm 41, pivoted at 42, and by virtue of damper rod 43 pivoted at 51 and passing through guide 44, to raise damper 16 from its normal position of contact with string 1. Bar 45, supported by rods 46 pivoted as at 47, may pass under the several arms 41 and connect by rod 48 to pedal 49, pivoted as at 50; depression of pedal 49 thus raising all the dampers l6 simultaneously from the strings 1, according to principles well known in the art. The dampers 16 are intended to perform the usual function of either fully permit-1 ting or eificiently preventing vibration of the associated strings. Excepting as to dampers 16, the term damping and its derivatives are herein employed in their broader sense, denoting decay of a vibration, or its decrease with time, whether inherent in a particularly mount vibrator or otherwise caused.

In Figures 1 and 2 I show representative further portions of a musical instrument of the class described, together with electrical means for regulating the damping of the vibrators, either increasing or decreasing the rate or such damping or completely neutralizing the same. Thus I show electrically conductive bar 8, which may be insulatedly mounted above strings I by uprights l0 and insulating blocks- 3. Below each string may be provided an elctro-mechanical translating device 11, comprising for example bar magnet 12 and coil 13, adjustably mounted in block 14 by set-screw 15. Bar 8 may be electrically connected to the grid of a thermionic vacuum tube 21, which I show in Figure 1 as the first tube of an electrical amplifier including tubes 22, 23 and 24, the last two being shown in push-pull arrangement. Battery 25 is shown for exciting the filaments or cathodes of tubes 21 and 22 and battery 26 for those of tubes 23 and 24. Battery 39 may serve as a source of anode current for tubes 23 and 24 and, in reduced potential if desired, for tubes 21 and 22. It will be understood, of course, that tubes with unipotential cathodes and A. C. current sources therefor, or other sources with tubes as shown may be substituted if desired; likewise that an A. C. operated current supply device may be substituted for battery 39. The filaments or cathodes of tubes 21 and 22 may be connected to the negative terminal of battery or source 39 through condensively lay-passed resistor 29 for the biasing, through resistor 27 and potentiometer 28 respectively, of their grids, negatively with respect to their cathodes; likewise the filaments or cathodes of tubes 23 and 24 may be connected to such negative terminal through condensively by-passed resistor 30. A different potential from that of bar 8 may conveniently be applied to strings 1 by connection of one of the triangular bars 6 to a point of positive potential in battery or source 39.

A. C. voltages applied to the grid of tube 21 appear in amplified form across resistor 31 in the output circuit of that tube and are applied through stopping condenser 32 to potentiometer 28, whereby they maybe selectably reduced in amplitude and applied to the grid of tube 22. Again amplified by tube 22 and push-pull transformer 33, they are applied to the grids of tubes 23 and 24, in equal amplitudes but in opposite phases on such two grids, as will be understood. In the output circuit of these tubes is connected loudspeaker 35, through the medium of transformer 34 if desired. 4

Connected to the anode of tube 23 I show a resistance element 36 and to the anode of tube 24 a resistance elementS'l; on each of these may be provided a slider 38, or a single slider may be employed as shown, which may be positioned at will anywhere .on either one or the other of such two elements. Such slider, or sliders connected together, as one terminal, and a point of mean A. C. potential between the two tube anodes as a second terminal, may connect to the electrical extremities of the group of translating devices 11, which among themselves are preferably connected in series aidingi. e., so that all exert a similar force, either of repulsion or attraction, on the associated strings upon the traversing of the series by any given electrical impulse.

If now one of the keys 1'? be depressed, causing the associated hammer 7 to be propelled toward the associated string 1 and the associated damper 16 to be raised therefrom, such string 1 will vibrate at its fundamental and harmonic frequencies, producing an oscillatory variation in the minute electrical capacity between such string 1 and bar 8. This capacity in parallel with other similar capacities forms a series circuit with resistor2'7 and a source of D. C. potential; it is therefore charged to the potential of the source, but its charge is prevented from changing rapidly by the resistor 2'7. By virtue of this relative constancy of charge, the abovementioned oscillatory variation of the stringbar capacity will produce across the capacity and hence across the resistor an A. C. voltage substantially corresponding in its various characterstics, including harmonic structure, to the vibration of the mean point of the string below bar 8. This voltage will be amplified by the succeeding thermionic apparatus as above outlined, and translated into sound by the loudspeaker 35. Such amplified voltage may also be applied, in amplitude and phase regulable by resistance elements 36 and 37 and slider or sliders 38, to the electro-mechanical translating devices 11. Each of these translating devices is thus caused to tend to vibrate its associated string at the fundamental and harmonic frequencies of the single string 1 first assumed to be vibrated. All of the strings, except this one, being efllciently prevented from vibrating by the dampers 16, no free vibrations thereof can take place as a result of this vibrating force; with respect to the one string from which the damper has been lifted, this tendency to vibrate will reinforce or oppose the exciting vibration,

depending on the phase relations as determined by the characteristics of amplifier and translating devices and by the settings of the slider or sliders 38.

If a plurality of keys 1'7 be simultaneously depressed and a pluralityof strings I thus freed of the associated dampers 16 and caused to vibrate. not only will a composite voltage corresponding to the algebraic sum of the several string vibrations appear in the amplifier and be translated into sound by the loudspeaker, but each of such strings will be subjected to a vibrating force containing components of its fundamental and harmonic frequencies. In general, due to the similarity between different strings of the arrangement of the electro-mechanical translating devices, a setting of the slider or sliders 38 to produce a reinforcement of the vibration of one string will be such as to provide reinforcement, and not opposition, of the vibration of the others. Each of the several strings whose keys are depressed will also, of course, be freed by their respective dampers and may respond somewhat in diaphragm fashion to all the frequency components of the vibrating force. Such response will be of a much lower order than the response to the natural frequency components of the string, and furthermore will be seen to introduce no foreign tones into the sound produced by the loudspeaker.

While I have shown and prefer to employ the resistance elements 36 and 3'7 electrically separate from each other with a single contact 38 operable over both, they may be joined together electrically to form a continuous single element. Their action is then that of a potentiometer instead of that of variable series resistances, as will be understood. In either case any given amplitude of vibrating force may be obtained in each of two .opposite phases, these being respectively available when slider 38 is separated first from the anode of one and then from that of the other of tubes 23 and 24 by a similar value of resistance. Furthermore by progressive settings of the slider 38 on the resistance elements or element between one anode and the other, a change in amplitude of vibrating force from very high to low or zero, and therefrom to very high in respectively opposite phase, in obtainable. Undue phase shifts being avoided in the inter-tube couplings, as is well understood in the art, and phase shifts due to inductancein the translating devices 11 being kept low by the employment of separate resistances 36 and 3'1 or a high resistance potentiometer in place thereof, it is readily possible by adjustment of the slider 38 to provide more than sufficient, just enough, or slightly less than enough vibrating force to sustain any string 1 in continuous vibration; to provide smaller aiding amplitudes of vibrating force or none'at all; or to provide small or great forces counteracting the original vibration of the strings and resulting in slightly or greatly increased rate of damping, respectively.

The adjustability in respect of proximity to the that position which, with similar strong hammer 159 impacts, is either just sufficient or preferablyjust less than sufiicient to maintain vibration of the respectively associated strings.

I consider it preferable to mount the mechanico-electric and the electro-mechanical translating devices-e. g., the bar 8 and the devices 11 as shownopposite the same portion of each string or vibrator in order that the feed-back or vibrating force may in general coincide in harmonic distribution with the vibration of the point or region to which it is applied; such relative positioning between the translating devices may be varied however if desired. I further prefer to employ the novel arrangement of two dissimilar devices-e. g., electrostatic and electromagnetic devices respectively as shown-in order to avoid direct transfer of energy from one device to the other. Other respectively dissimilar forms may likewise be employed, of course. For the further avoidance of this effect I show in Figure 2 a shield '71 above the coils of the devices 11, such shield, and the magnets 12 by virtue of contact thereto, being conveniently grounded to one of the triangular bars 6 for establishment thereof at the potential of the strings. It will be understood, however, that such dissimilarity of form of the respective devices is not necessarily imperative; and furthermore that the electrostatic and electromagnetic forms may be interchanged in position or respective function and that other forms may be substituted for either or both.

For the avoidance of undue sensitivity. or susceptibility of the entire instrument to stray electrostatic fields, I show in Figure 1 shielding '70 disposed about the electrical amplifier, partially about the strings, translating devices and associated equipment, and about the electrical connections between the two. Such shielding may conveniently be grounded to the potential of strings 1. i

It will be understood, of course, that the electro-mechanical translating devices need not be connected to the very output of the amplifier, as in Figure 1; they may be connected to any point in the amplifier where suflicient amplification of the voltage generated in the mechanico-electric translating device has occurred. Furthermore an amplifier entirely separate from that actuating the loudspeaker 35 may be employed to energize these devices, the input of such separate amplifier being connected either to the same or to a difierent mechanico-electric translating device as or from that connected to the input of the loudspeaker-actuating amplifier, Thus in Figure 3 I show schematically a plurality of strings 1, a hammer 7 for each, a mechanicoelectric translating device comprising bar 8, a battery 32, and resistor 2'? as in Figure 1; an amplifier 30, a center-tapped potentiometer 81 preferably of high resistance, and translating devices 11 connected to the potentiometer. The function of this system is purely the regulation of the amplitude-time vibration characteristics of the strings 1, its manner of functioning being similar to that described above. A separate bar 82, a resistor 84, an amplifier 85 and a loudspeaker 35 may provide the mechanica-electric-acoustic translation for the actual production of music by the instrument, as will be understood. Such separation of function-4. e., use of a separate system for amplitude-time characteristic regulation-is particularly suitable when it is desired to employ in the music production a plurality of mechanico-electric translating devices associated with different portions of each vibrator, as for tone variation purposes.

. and

Various modifications not hereinabove specifically mentioned may of course be made by those skilled in the art. gree of amplification than illustrated may be employed; other tuned vibrators may be substituted for the strings, other forms of vibrator excitation than hammer percussion employed, etc., as will be understood. Modification of the methods and apparatus disclosed in these and other respects will not necessarily constitute a departure from the spirit or scope of my invention, as hereinabove described and in the appended claims defined.

I claim:

1. In a musical instrument, the combination oi a plurality of variously tuned vibrators; a mechanico-electric translating system having portions respectively in spaced relationship to said vibrators and being arranged to produce electric oscillations in accordance with vibratory variations of such spaced relationships; a single electrical amplifier connected in the output circult of said mechanico-electric translating system for collectively amplifying said oscillations;

an electro-inechanical translating systern connected in the output circuit of said amplifier, said system having portions disposed in spaced relationship to said vibrators and arranged to exert on all of said vibrators forces of attraction and repulsion in accordance withv said amplified oscillations.

2. In a musical instrument, the combination or" a plurality of variously tuned vibrators; selective means for initiating vibrations thereof; a mechanico-electric translating system having portions respectively in spaced relationship to said vibrators and being arranged to produce electric oscillations in accordance with vibratory variations of such spaced relationships; at single electrical amplifier connected in the output circuit'of said mechanico-electric translating systern for collectively amplifying said oscillations;

and an electro-mechanical translating system connected in the output circuit of said amplifier, said system having portions disposed in spaced relation to said vibrators and arranged to exert on all of said vibrators forces of attraction and repulsion in accordance with said amplified oscillations.

3. In a musical instrument, the combination of a plurality of variously tuned vibrators; damping means for preventing vibration thereof; means selective with respect to said vibrators for releasing said damping means; a niechanicoelectric translating system having portions respectively in spaced relationship to said vibrators and being arranged to produce electric oscillations in accordance with vibratory variations oi such spaced relationships; a single electrical amplifier connected in the output circuit of said mechanico-electric translating system for collectively amplifying said oscillations; and an Thus a greater or smaller de-. I

la-ting system having portions respectively in spaced relationship to said vibrators and being arranged to produce electric oscillations in accordance with vibratory variations of such spaced relationships; a single electrical amplifier connected in the output circuit of said mechanico-electric translating system for collectively amplifying said oscillations; and an electromechanical translating system connected in the output circuit of said amplifier, said system having portions disposed in spaced relationship to said vibrators and arranged to exert on all of said vibrators forces of attraction and repulsion in accordance with said amplified oscillations.

5. In a musical instrument, the combination of a plurality of variously tuned vibrators; a mechanico electric translating system having portions respectively in spaced relationship to said vibrators and being arranged to produce electric oscillations in accordance with vibratory variations of such spaced relationships; a single electrical amplifier connected in the output circuit of said mechanico-electric translating system for collectively amplifying said oscillations; and an electro-mechanical translating system connected in the output circuit of said amplifier, said system having portions disposed in spaced relationship to said vibrators and arranged to exert on all of said vibratorsrforces of attraction and repulsion in accordance with said amplified oscillations; and means preceding said electromechanical translating system for regulating the phase of oscillations thereto supplied.

6. In a musical instrument, the combination of a plurality of variously tuned vibrators; a mechanico-electric translating system having portions respectively in spaced relationship to said vibrators and being arranged to produce electric oscillations in accordance with vibratory variations of such spaced relationships; a single electrical amplifier connected in the outputcircuit of said mechanico-electric translating system for collectively amplifying said oscillations; an electro-mechanical translating system connected in the output circuit of said amplifier, said system having portions disposed in spaced relationship to said vibrators and arranged to exert on all of said vibrators forces of attraction or repulsion in accordance with said amplified oscillations; and means interposed between said translating devices for reducing direct energy transfer therebetween.

'7. In a musical instrument, the combination 01' a plurality of variously tuned vibrators; a mechanico-electric translating system having portions respectively in spaced relationship to said vibrators and being arranged to produce electric oscillations in accordance with vibratory variations of such spaced relationships, a single electrical amplifier connected in the output circuit of said mechanico-electric translating system for collectively amplifying said oscillations; an electro-mechanical translating system connected in the output circuit of said amplifier, said system having portions disposed in spaced relationship to said vibrators and arranged to exert on all of said vibrators forces of attraction or repulsion in accordance with said amplified oscillations; and adjustable "means individually associated with said portions of said electromechanical translating system for securing said portions, whereby their several said spacings from said vibrators may be individually adjusted.

8. The combination of a tuned vibrator a translating device of electrostatic form comprising a conductive element positioned in spaced relationship to said vibrator to form therewith an electrical capacity and means for maintaining a relatively constant charge in said capacity; a translating device of electromagnetic form comprising a magnetic circuit, a magnet in said circuit in spaced relationship to said vibrator, and a coil threaded by said circuit; and an electrical amplifier electrically interposed between said devices, whereby one of said devices is caused to operate as mechanico-electric, and the other as an electro-mechanical, translating device.

9. In a musical instrument, the combination of a tuned vibrator; a source of electric oscillations; a work circuit; a translating device of electrostatic form comprising a conductive element positioned in spaced relationship-to said vibrator to form therewith an electrical capacity and means for maintaining a relatively constant charge in said capacity; a translating device of electromagnetic form comprising a magnetic circuit, a magnet in said circuit in spaced relationship to said vibrator, and a coil threaded by said circuit; one of said devices being arranged as an electro-mechanical translating device to translate said oscillations into vibration of said vibrator and the other of said devices being arranged as a mechanico-electric translating device to translate vibrations of said vibrator into electric oscillations in said work circuit.

' BENJAMIN F. MIESSNER. 

